1. Technical Field
This invention relates to supplying coolant to a location of contact between a workpiece and a material removing tool, and more particularly, relates to supplying coolant to grinding operations.
2. Background Information
It is known to equip a grinding machine with a nozzle which can discharge one or more jets, sprays or streams of a suitable liquid coolant to the location of contact between a workpiece and a material removing tool, such as a rotary grinding wheel. The nozzle can be trained or aimed upon the location of contact and is connectable to a source of coolant, e.g., by a hose. Such cooling of the location of contact between a workpiece and a grinding tool beneficially affects the quality of the finished product. This is especially in a modern grinding machine wherein the tool is expected to remove large quantities of material from a workpiece, where inadequate cooling may damage the surface integrity of the workpiece material.
It is further known to design a nozzle in such a way that it can supply adequate quantities of coolant in suitable distribution to the location of contact between a relatively large surface of a workpiece and a suitably profiled working surface of a rotary grinding wheel or an analogous tool. The nozzle may satisfy the requirements regarding the delivery of adequate quantities of coolant in optimum distribution as long as the particular grinding tool remains installed in the machine and as long as such tool is in the process of removing material from a particular series of workpieces. If the particular grinding tool is replaced with another tool of differing profile, or if another profile of the same tool is moved into material removing contact with a workpiece, the nozzle may no longer ensure optimal withdrawal of heat from workpieces. Thus, it is generally necessary to replace the nozzle with a different nozzle in a time-consuming operation which may entail long periods of idleness of the machine. This situation is aggravated if several different profiles of a particular workpiece are to be treated by a set of different tools or by two or more sets of different tools. This necessitates the removal of a previously used grinding tool from the machine.
An additional factor that affects the quality of workpiece cooling is the dispersion of the coolant jet applied to the workpiece. Dispersion has been shown to be disadvantageous because it tends to increase entrained air, and air tends to exclude some coolant from the grinding zone (i.e., grinding wheel/workpiece interface). Dispersion also tends to reduce the accuracy of the aim of the coolant jet, allowing fluid to miss and/or bounce away from the grinding zone. Dispersion may be reduced by the use of relatively long straight sections of hose/tubing immediately upstream of the nozzle. This, however, is impractical in many applications due to the space limitations of many grinding machine installations. In an attempt to overcome this limitation, plenum chambers have been disposed immediately upstream of the nozzle. The relatively large cross-sectional area of the plenum was intended to slow down the coolant velocity and allow it to stabilize before accelerating from the nozzle exit aperture, to improve coherence in applications in which long, straight upstream pipe portions are impractical. However, the relatively large size of such plenum chambers makes them difficult to locate close enough to the grinding zone to provide optimal cooling in many applications.
It has also generally been found that the quality of workpiece cooling may be improved by matching the velocity of the coolant jet to that of the grinding surface of the grinding wheel. To achieve velocity matching, and to minimize dispersion and entrained air, it has generally been found that the jet should reach the grinding zone within about 12 inches (30.5 cm) from the nozzle.
A need exists for an improved coolant nozzle capable of providing coherent jets, and which is easily adjustable to provide optimal coolant flow in a variety of grinding applications and distances from the grinding zone.
According to one aspect of the invention, a nozzle assembly is provided, which includes a plenum chamber, and a modular front plate removably fastened to a downstream side of the plenum chamber. The assembly also includes at least one coherent jet nozzle disposed for transmitting fluid through the modular front plate, and a conditioner disposed within the plenum chamber.
In another aspect of the invention, a nozzle assembly includes a plenum chamber having a non-circular cross-section in a direction transverse to a downstream fluid flow direction therethrough, at least one coherent jet nozzle disposed at a downstream end of the plenum chamber, and a conditioner sized and shaped to substantially match the cross-section, which is disposed within the plenum chamber.
In yet another aspect, a nozzle assembly includes a plenum chamber configured to pass coolant in a downstream fluid flow direction therethrough, and a plurality of coherent jet nozzles disposed at a downstream end of the plenum chamber.
In a still further aspect, a nozzle assembly includes a plenum chamber, a modular card removably fastenable to a downstream side of the plenum chamber, at least one coherent jet nozzle disposed within the card for transmitting fluid from the plenum chamber therethrough, and a conditioner disposed within the plenum chamber.
Another aspect of the invention involves a method for delivering a coherent jet of grinding coolant to a grinding wheel. The method includes determining a desired flowrate of coolant for a grinding operation, and obtaining a grinding wheel speed at an interface of a grinding wheel with a workpiece. The method further includes determining coolant pressure required to generate a coolant jet speed that matches the grinding wheel speed, determining a nozzle discharge area capable of achieving the flowrate at the pressure, and determining a nozzle configuration.
In another aspect of the present invention, a grinding tool kit includes a dressing roller sized and shaped to impart a profile to a grinding wheel, and a dressing module sized and shaped for being coupled to a plenum chamber. The dressing module includes a plurality of coherent jet dressing nozzles which are sized and shaped for supplying coolant from the plenum chamber to a dressing zone of the grinding wheel. The kit also includes a grinding module sized and shaped for being coupled to another plenum chamber. The grinding module includes a plurality of coherent jet grinding nozzles which are sized and shaped for supplying coolant from the other plenum to a grinding zone of the grinding wheel.